(a) Field of the Invention
The present invention relates to a fuel cell stack, and more particularly, to a fuel cell stack in which that temperature deviation between cells is reduced.
(b) Description of the Related Art
A fuel cell stack is an electric power generating device that generates electrical energy through an electrochemical reaction between hydrogen and oxygen in respective fuel cells thereof, and is applied to a fuel cell vehicle, etc. Further, the fuel cell stack is a fuel cell assembly in which fuel cells are arranged sequentially. The fuel cell is a unit cell in which a separator is respectively disposed at opposite sides of a membrane-electrode assembly (MEA) with the MEA disposed therebetween. The fuel cells may be fastened with end plates and fastening members in a pressed state.
As mentioned, the fuel cell stack as described above generates electrical energy through an electrochemical reaction of hydrogen and oxygen, produces heat and water which are by-products of the electrochemical reaction, and is cooled by a coolant which is a cooling medium. In the fuel cell stack, a temperature distribution of the fuel cells should be uniformly maintained within a predetermined range. An end plate provided with a current collector is positioned at each of the opposite ends of the fuel cell stack, and a temperature of a cell (hereinafter, referred to as an “end cell”) in the vicinity of the end plate is less than that of other cells.
A temperature deviation between the cells of the fuel cell stack occurs mainly during the cold-starting or the cold-driving of the fuel cell stack, and is caused due to the heat generated in the end cell being absorbed by components (e.g., the end plate and the current collector) having a substantially large heat capacity around the end cell and thus, a temperature rise of the end cell is delayed. Due to a low temperature of the end cell, reaction gas may be excessively humidified to cause flooding at the end cell. Accordingly, the reaction gas is supplied insufficiently at the end cell for a voltage of the cell to decrease, thus an output of the fuel cell stack may be limited. In order to improve the temperature deviation between the cells of the fuel cell stack, Korean Patent Laid-Open Publication No. 2014-0024776 and Korean Patent Laid-Open Publication No. 2014-0086150 are filed by the applicant.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.